1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device and, more particularly, relates to a semiconductor device having a chip scale package (hereinafter referred to as CSP) structure and to a method of manufacturing the semiconductor device.
2. Background Art
It is a recent trend that electronic equipment has been smaller and lighter, and under such a trend, smaller and lighter semiconductor packages have been increasingly demanded as a matter of course.
CSP is a general term of a package size equal to or slightly bigger than size of a semiconductor chip. Generally, CSP has a structure in which semiconductor chips are mounted on a package base of a size equal to or slightly bigger than the size of the semiconductor chips. Electrodes of the semiconductor chips and those of the package base are electrically connected, and they are sealed with a resin.
The CSP has been conventionally formed by a method in which a semiconductor wafer is cut into semiconductor chips, then the semiconductor chips are mounted on a substrate serving as a package base at predetermined positions and bonded thereto, and they are collectively sealed with a resin, thereafter the sealing resin and the substrate are cut into pieces together at the parts between the semiconductor chips. In another conventional method, a semiconductor wafer (not being cut into semiconductor chips yet) is mounted on a substrate and bonded thereto, then the semiconductor wafer and the substrate are cut together, and the cut and divided semiconductor chips and package bases are sealed with a resin. However, in the former conventional manufacturing method, a problem exists in that the method essentially includes a step of positioning and mounting the cut and divided semiconductor chips one by one on the substrate. Like wise in the latter conventional manufacturing method, a problem exists in that the method essentially includes a step of sealing the cut and divided semiconductor chips and package bases one by one with a resin. Both conventional methods require a number of working processes equal to the number of semiconductor chips, which results in a disadvantage of low productivity.
To overcome the foregoing problems, Japanese Patent Publication (unexamined) No. Hei 9-232256, and Japanese Patent Publication (unexamined) No. 2001-35972 proposed a method of forming a semiconductor device having a CSP structure. The proposed method includes the steps of mounting and bonding a semiconductor wafer (not being cut into semiconductor chips yet) on a substrate, cutting only the semiconductor wafer into semiconductor chips, filling spaces between the cut semiconductor chips as well as between the semiconductor chips and the substrate with a sealing resin, and then cutting together the sealing resin and the substrate between the semiconductor chips at the same time.
Further the Japanese Patent Publication (unexamined) No. 2001-35972 proposed a method of forming a semiconductor device having a structure. In this proposed method, at the time of cutting the semiconductor wafer into semiconductor chips, a part of the substrate is also cut and filled with a sealing resin at the same time. Thus not only side faces of the semiconductor chips and parts between the semiconductor chips and the package bases but also a part of side faces of the package bases are sealed with a resin.
In the mentioned conventional semiconductor device having a CSP structure and proposed for the purpose of reducing number of working processes, a semiconductor wafer is cut into semiconductor chips in the state of mounting the semiconductor wafer on the substrate, and the sealing resin for filling the spaces formed by cutting the semiconductor wafer is used as a sealing material when the semiconductor chips are divided into separate pieces. Therefore, dicing lines that include a sealing resin must be provided on the semiconductor wafer at the parts between the individual semiconductor chips to be formed, and this causes a problem of reducing number of semiconductor chips obtained from one wafer.
Moreover, the sealing with a resin is performed in the state that the substrate on which the semiconductor chips are mounted is not completely cut, and therefore side faces (cut faces) of the package bases formed by cutting the substrate remain not sealed with the resin. Thus another problem exists in that the semiconductor device formed by such manufacturing method is low in reliability due to moisture absorption from the side faces of the package bases and so on.
The present invention was made to resolve the above-discussed problems and has an object of providing a highly reliable semiconductor device and a method of manufacturing the semiconductor device, in which number of working processes can be reduced without decreasing number of semiconductor chips obtained from one piece of wafer, thus productivity being improved.
To accomplish the foregoing object, a semiconductor device according to the invention includes: semiconductor chips mounted on package bases; electrode pads provided on the semiconductor chips; and connecting electrode pads provided on the package bases; the electrode pads being electrically connected to the connecting electrode pads: and
in which spaces where the semiconductor chips and the package bases are joined together are filled with a sealing resin; and side faces of the semiconductor chips and side faces of the package bases are continuously coated with the sealing resin.
As a result of such a structure, cut faces of the base member forming the package bases of which hygroscopicity tends to be relatively high are not exposed, and the portions where the semiconductor chips and the package bases are joined together are protected by the sealing member. Therefore, not only the semiconductor device becomes highly moisture-resistant, but also strength of the portions where the semiconductor chips and the package bases are joined together is increased. Consequently it is possible to obtain a highly reliable semiconductor device.
A method of manufacturing a semiconductor device according to the invention includes the steps of: positioning and mounting a semiconductor wafer, where a large number of semiconductor chips are formed, on a substrate, where large number of package bases are formed, and flip-chip-bonding electrode pads respectively provided on the semiconductor chips and connecting electrode pads respectively provided on the package bases; mounting the flip-chip-bonded semiconductor wafer and substrate on a dicing sheet and cutting and dividing the semiconductor wafer and the substrate into semiconductor chips; filling with a sealing resin spaces between adjoining semiconductor chips as well as between adjoining package bases and spaces where the bonded semiconductor chips and package bases are joined, while expanding the dicing sheet thereby expanding spaces between the cut semiconductor chips; and cutting the large number of bonded semiconductor chips and package bases sealed with the resin into separate pieces of semiconductor chips with the sealing resin left on both sides of cut faces.
As a result of such manufacturing process, the semiconductor wafer formed with the large number of semiconductor chips is positioned and mounted on the substrate formed with the large number of package bases, and the semiconductor chips and the package bases are collectively sealed with a resin. Consequently, any working process such as handling and bonding the semiconductor chips one by one is no longer necessary, thus the productivity is improved. Furthermore, after the bonded semiconductor chips and package bases are cut into separate pieces, the spaces for forming the sealing resin necessary for the semiconductor device are provided between the adjoining semiconductor chips by the expanding process. Accordingly, at the time of forming the semiconductor chips on the wafer, it is not necessary to provide any space for forming the sealing resin between the adjoining semiconductor chips. Therefore, number of semiconductor chips obtained from one piece of wafer is increased as much resulting in improvement of production efficiency. Thus the invention can provide a highly productive manufacturing method of a semiconductor device.